According to Patent Literature 1, a widely known drum brake is based on a device in which a strut is arranged in a space between one facing ends of a pair of brake shoes, and a quadrant is positioned at one end of the strut body such that the quadrant is rotatable and movably pivoted in a longitudinal direction of the strut body, the quadrant having a shoe engagement portion (projecting arm) formed at one end thereof engaging, with a predetermined gap, a quadrant engagement portion (quadrant engagement hole) formed at a shoe web of one brake shoe, and the quadrant rotating to adjust a brake shoe clearance automatically when the amount of brake shoe outward movement exceeds a predetermined value, where an anti-rattle spring is extended between the strut and the other brake shoe and a quadrant spring is extended between the strut body and the quadrant.
Also, according to Patent Literature 2, another widely known drum brake is based on a device in which a shoe engaging portion of the quadrant is a projection from one side surface of the quadrant, and a quadrant engagement portion of the shoe web is a notched groove formed on the shoe web.
In this structure, there must be two springs, i.e., an anti-rattle spring functioning as a first adjuster spring and a quadrant spring functioning as a second adjuster spring, which increases the parts cost and the entire manufacturing cost because of an additional assembly process required for the spring installation.    [Patent Literature 1] Japanese Provisional Patent Publication No. 59-126127    [Patent Literature 2] European Patent Publication No. 0462731